Electromagnetic earphone receiver



SebtQ 21, 1.948.

w. F. KNAUERT ELECTROMAGNETIC EARPHONE RECEIVER Filed Feb. 4, 1944 INVENTOR W/LA/AM /-T KNAUEE'T M q a,

ATTORNEYS Patented Sept. 21, 1948 ELECTROBlAGNETIC EARPHONE RECEIVER William F. Knauert, Yonkers, N. Y., assignor to Sonotone Corporation, Elmsford, N. Y., a corporation of New York Application February 4, 1944, Serial No. 521,007

1 This invention relates to earphone receivers, and particularly to midget-size earphones of the type in which the vibratory diaphragm forming Among the objects of the invention is an improved earphone receiver of the foregoing type, the electro-transducing structure of which has a continuous, circular seating ridge projection engaging a peripheral region of the diaphragm which is inwardly spaced from its edge, the seating ridge having depressed inner and outer circular regions adjoining the circular surface region which engages the diaphragm so as to give the ridge portion facing the diaphragm a curved convex cross-section and assure that under all operating conditionsa raised circular region of the seating ridge shall maintain engagement with the continuous peripheral region of the diaphragm.

Another phase of the invention is the manufacture of such earphone receivers, involving the steps of determining the frequency response characteristics of the receiver diaphragm which is to be used in a given receiver, and machining the seating ridge projection of the given receiver with such diameter as to cause the diaphragm to operate with a resonant frequency at which the acoustic transmitting space exhibits predetermined desired frequency response characteristics.

The foregoing and other objects of the invention will be best understood from the following description of exemplifications thereof, reference being had to the accompanying drawings in which Fig. 1 is a vertical cross-sectional view of a midget earphone receiver exemplifying one form of the invention, in a position in which it is held against the ear of the user;

Fig. 2 is a View along line 2-2 of Fig. 1 with the cover and diaphragm of the receiver removed;

Fig. 3 is a greatly enlarged detailed view similar to Fig. 1 showing a peripheral portion of the receiver diaphragm and its seat arrangement;

Fig. 4 is an enlarged view showing the relative positions of the receiver and a ridge-cutting tool used for machining the diaphragm seat of the receiver;

Fig. 5 is a view similar to Fig. 1 illustrating a receiver of the invention equipped with a modified form of electromagnetic driving mechanism; and

"Fig. 6 is a rear view of the electromagnetic unit of Fig. 5.

Referring to Figs. 1 to 3, the earphone com prises an electro-acoustictransducing structure 5 Claims. (Cl. 179--114) 2 having its driving elements supported by a circular aligning member I I, which is shown formed of a cylindrical shell of metal, such as brass, having on its outer open side an enlarged circular rim portion 12 provided with a flanged outer region forming a cover seating shoulder l3, the exterior of which is threaded so that the cover wall M with its outlet duct 15 may be positioned and held thereon in the spaced position which is fixed by the height of the seating shoulder [3 as shown. a e

In the interior of the cylindrical shell H are held a segmentally-shaped permanent magnet block I1 and a pole member [8 having an eccentrically arranged pole piece I 9 projecting into the open side of the shell ll so as to concentrate a strong permanent magnet flux in the central space region between the outward end of the pole piece l9 and the adjacent edge region l9--l of the permanent block segment H, which serves as the other pole of the magnetic driving core structure. The permanent magnet block I! and the pole member 18 are suitably secured, as by soldering, to each other and to the shell H so that the pole ends of the pole member l8 and permanent magnet block I! are held in positionssuitably aligned with respect to the surface e1ements of the aligning rim I 2. A winding 20 in the form of a spool mounted on the pole piece l9 serves to actuate the receiver.

The aligning member i2 has an outwardly facing surface It which is provided with a continuous, generally ci-rcular, outwardly-projecting seating ridge 2| against which a peripheral region of the inner side of a diaphragm 23 rests. The diaphragm 23 is self-supporting and may be made of a flat spring'metal plate. The central part of the diaphragm 23 is arranged to serve'as a magnetic armature for cooperation'with the pole portions I9, l9-'-l of the magnetic driving structure, so that the diaphragm shallvibrate over'the principal audio-frequency range under the action of corresponding electric oscillatory currents send through the receiver windings 20. The cover' seating shoulder [3 has height sufliciently greater than the diaphragm seating ridge so as to provide on the exterior side of the vibrating diaphragm an acoustic space predetermined acoustic characteristics and which serves to control the frequency response of the receiven In the arrangement shown, the central magnetic armature portion of the diaphragm is provided with the required magnetic cross-section by uniting'to it, as by soldering, a central magnetic plate element '24. The permanent magnet block I? is designed 'to produce a permanent flux strong enough to assure that the unidirectional magnetic forces, exerted by the flux in the pole region on the central portion of the diaphragm 23, will hold its periphery firmly pressed against and maintainit in engagement with the underlying surface of the aligning rim [2.

In the past, earphone receivers of the type utilizing a floating diaphragm, the rim of which is held in its operative position solely by attractive forces exerted by the electro-mechanicai driving structure on the central diaphram portion,

have given a great deal of trouble because they exhibited disturbing and annoying buzzing due to 25. of the seating ridge 2| is adjoined' by depressed inner and outer circular regions 26, 2.1, respectively, arranged so as to give the circular surface portion of the ridge facing the diaphragm a curved convex cross-section and assure that a raised circular; region of the seating ridge shall at all times maintain seating engagement with a continuous inwardly-spaced peripheral region of the diaphragm in all of the vibratory positions to which it is brought by the varying forces exerted thereon.

The diaphragm seating arrangement of the invention is so designed as to assure that a peripheral regio rr of the diaphragm, which, is spaced from its outer edge, will engage a continuous circular-region of the curved raised. ridge surface in all the vibratory positions of the diaphragm throughout the normal range of its vibratory amplitudes. Such diaphragm seating arrange-. ment of the invention makes it possible to opera-te a receiver diaphragm of only about /4 inch diameter with. very large amplitudes, as much as about .005 inch, without undue distortion, and to supply with a tiny receiver, using suchsmall diaphragm, as much output as with a receiver which is a multiple of its size.

The receiver arrangement of the invention de scribed above in connection with a specific exemplification thereof, has also the further ad'- vantage that it makes possible the manufacture of receivers. with uniform predetermined desiredresponse characteristics, notwithstanding the fact that the individual receivers have to be operated with diaphragms differing in their resonant frequencies.

In accordance with the invention, a series of receivers having acoustic sound-transmitting spaces of desired predetermined frequency response characteristics may be manufactured by determining the frequency response characteristics of the. receiver diaphragms which are to be used in a given receiver, a machining the seats, ing ridge projection of the iven receiver with such diameter-as to'cause the diaphragm to. op.-v erate with a r s nant frequency at wh c t acoustic transmitting space formed between the cover wall with its sound outlet duct I5 and the vibratory diaphragm 2:3 exhibits th esired fr qu ncy resp nse charact r st In other words, by making th c rcular rid 2,1 of greater or smaller diameter, depending on the characteristics of the diaphragm which is tobe used in a given receiver, the different receivers, although having diaphragms of different response characteristics, maybe readily manufactured on a mass production basis so that th y .831 pegete with the same predetermined response characteristics.

The receiver assembly with its diaphragm supporting rim i2 is provided. with an outwardly facing surface lB-l extending along a higher level than the surface IS on which the raised seating ridge 2| is formed, as indicated in Fig. 4. The receiver assembly shown in Fig. 4 has its circular surface I6-lmachined off as in a lathe operation, byacutting tool 3| provided with a radially disposed cutting edge 32 extendin over substantially the entire radial width of the surface l6l and having on its cutting edge 32 a notch 33 so as to reduce by a rotary cutting operation the height of the rim l2 and form on it the raised ridge 2! as well as the adjoining lower surface region IS. The cutting tool 3| is also sh0wn.pr0-. vided along its radially inward edge region with stop surface portion 32..l.

The stop. surface portion 32l is designed to come into engagement with the flat pole faces of the, pole piece end I9, and of the adjacent pole portion l9,-l for stopping the cutting action. in a. predetermined position at which the raised seating surface 25 of the seating ridge 2| is at such level with respect to the level of the pole faces as. to assure the proper magnetic gapconditions between the pole faces and the facing central armature portion of the diaphragm 23 required for efficient operational the receiver with the required frequency response characteristics,

The machining of the seating ridge 2! with different diameters so as to compensate for dif-. ferences in the thickness of the diaphragms provide each diaphragm with a seating surface ridge of such diameter as to assure that it will operate with the desired resonance frequency which makes it possible to assure that all receivers having the same magnetic gap spacin will operate with the same desired frequency response characteristics,

By adjusting the radial position of the cutting tool- 3! relatively to the aligning rim l2, in the manner indicated by arrows 3 l--.2, the ridge may be formed on different radially-spaced peripheral regionsof the rim I2, thus. giving the raised seat? ing surface of the seating ridge different diameters, Very minute differences in, the diameter of the ridge, varying by only as little as .001 to.

.003-inch, are in most cases sufficient to compensate for differences in the resonant frequencies of the diaphragms resultin from slight varia-. tions in the thickness of the stock out of which the diaphragms are punched.

As shown in Figs. 1 and 2, theearphone is also provided with a casing shell member- 4| which does not perform any functions except to serve as an enclosure for theparts of the driving structure which are secured tothe aligning member H. In order to secure the casingshell M to the driving structure, the inner wall of its annular rim I2 is provided with two inwardly extending ear portionsv 12' which serve as seats for the flat heads of two clamping screws 43, the shanks of which engage bushing portions 44 of the casing wall ll.

The winding ends of the coil 20 are connected to two terminal bushings H which extend through and are affixed to a side wall portion of the casing shell so that when a cord'plug- 48- of the connecting cord is inserted in the terminal bushings M; the outwardly projecting plug portions shall not interfere with the insertion of the earphone into the space within the outer ear. As shown in Fig. 1, the portion of the cylindrical; casini;

5.. shell in'the region of the connector bushings 41 is cut away so as to expose the inner ends of the bushings 41 to the interior space of the shell H' in which the coil 20 is mounted. Y

The principles underlying the invention as described above in connection with one.specific exhaving their central pole arms aligned opposite the central region of the diaphragm 23, the wider rear portions 52 of the pole pieces extending on opposite sides of a permanent magnet bar lT-l and the pole piece portions 52 being united to the permanent magnet bar l'!-l and to the suitablydeformed rear end portions of the aligning member shell l|--|, as by soldering.

The central raised circular seating region 25 of the seating ridge may be coated with a thin layer of flexible sealing material, such as synthetic resin or synthetic rubber material. The entire circular seating ridge projection 2| may be made as a unit either of metal or of a synthetic resin materiahand suitably secured, as by soldering, fusion or cementing, in its proper position on the receiver structure.

Various other modifications of the invention will suggest themselves to those skilled in the art. It is accordingly desired that in construing the breadth of the appended claims they shall not be limited to the specific details shown and described in connection with the exemplifications of the invention.-

I claim:

1. 'In a telephone receiver: a vibratory diaphragm having a generally circular periphery; a cover wall including a sound outlet duct and extending over the outer side of the diaphragm and forming with it an acoustic transmitting space; a relatively massivevdriving structure comprising a substantially-rigid aligning member having a continuous,- generally-circular, outwardly-projecting rigid seating ridge of curved cross-section against which a peripheral region of the inner side of said diaphragm rests and an electroacoustic transducing structure secured to said aligning member and located opposite the inner side of said diaphragm; said transducer structure embodying means for exerting unidirectional forces on the central region of said diaphragm and for inducing with electric oscillations of the principal audio-frequency range corresponding vibratory forces exerted on said central region of said diaphragm; said seating ridge having a raised circular surface region engaged by a peripheral region of said diaphragm spaced radially inwardly away from the outer edge thereof; said diaphragm being held pressed against said seating ridge and being maintained in an operative vibrating position thereon solely by the magnetic forces which are exerted on the central portion of said diaphragm; said raised circular surface region of said seating ridge being adjoined by depressed inner and outer circular regions thereof arranged to give the portion of said ridge facing said diaphragm a curved convex cross-section which is so shaped that a raised circular region of said seating ridge shall maintain engagement with a continuous peripheral region of the diaphragm throughout the normal range of the vibratory amplitudes thereof.

2. In 'a telephone receiver: a vibratory diaphragm having a generally circular periphery and a generally central magnetic armature portion;

a cover wall including a sound outlet duct andextending over the outer side of the diaphragm and forming with it an acoustic transmitting space; a relatively massive driving structure comprising a substantially-rigid aligning mem-' ber having a continuous, generally-circular, outwardly projecting rigid seating ridge of curved cross-section against which a peripheral region of the inner side of said diaphragm rests and an electroacoustic transducing structure including magnetic core portions secured to said aligning member and located opposite the inner side of ing ridge and being maintained in an operative vibrating position thereon solely by the magnetic forces which are exerted by said core structure on the central portion of said diaphragm; said raised circular surface region of said seating ridge being adjoined by depressed inner and.

outer circular regions thereof arranged to give the portion of said ridge facing said diaphragm a curved convex cross-section which is so shaped that a raised circular region of said seating ridge shall maintain engagement with a continuous peripheral region of the diaphragm throughout the normal range of the vibratory amplitudes thereof.

3. In a telephone receiver:

tion; a cover wall including a scund-outletduct and extending over the outer side of the diaphragm and forming with it an acoustic transmitting space; a relatively massive driving structure comprising a substantially-rigid aligning member having a continuous, generally-circular, outwardly-projecting rigid seating ridge of curved cross section against which a peripheral region of the innerside of said diaphragm rests and an electroacoustic transducing structure including mag-- netic core portions secured to said aligning member and located opposite-the inner side of said dia; phragm; said core structure embodying pole elements for exerting unidirectional magnetic forces on the central region of said diaphragm; said transducer structure including windings for inducing with electric oscillations of the principal audio-frequency range corresponding vibratory magnetic forces exerted by said core structure on said central region of said diaphragm; said pole elements having fixed pole face portions spaced by a small gap from said armature portion; said seating ridge having a raised circular surface region engaged by a peripheral region of said diaphragm spaced radially inwardly away from the outer edge thereof so as to maintain said armature portion at a predetermined gap space range from said pole face portions; said diaphragm being held pressed against said seating ridge and being maintained in an operative vibrating position thereon solely by the magnetic forces which are a vibratory diaphragm having a generally circular periphery, and a generally central magnetic armature por-.

exerted onathecentralportion :of: saidldiaphragni said'raised circul ar surfac'eregion of said seating ridge being adjoined by depressed-inner andzcuter circular regions thereof: arranged ito give the pen tion of said rridge fa said diaphragm a curved convexx' cross section which is so shaped; that a' raiseda'circularregion of: said seating ridge shall maintain engagement with a" continuousperiph-- e al; regiom ofthe; diaphragm throughout the normal range of the vibratory, amplitudes'thereof 4%. In: a"- telephone receiver: a vibratory diaphragmihaving a generally circulai periphery; a.

coverrwall including a' soundoutlet: duct and extending over the outer side'of'the'diaphragm' and forming: with it an acoustic transmitting space; sa-irelatively massive driving structure comprising a substantiallyerigidi aligning member having: a" continuous. generally-circular, outwardlyeproje'cting rigid seating;ridge of curved cross'escction against which a peripheral region-of the; inner: side ofsaid'i diaphragm nests and anelectro' acoustic transducing:structure secured to saidialigning member located'opposite theinner" siderofi said diaphragm; said transducer structure embodying means for" exerting unidirectional forces ou the central region of said diaphragm and: for? inducing 'witht'electric oscillations of the principal audimf'requen'cy range corresponding vi bratory forces exerted on" said central region' or said diaphra'gm'; said seatingridge having a raised circulansurface'region engaged'by a peripheral* region'of s'aid'diaphragm spaced radiallyinwardly" away fromtheouter edgethereoi said diaphragm being held-pressed" against said seating ridge and beingimaintain'e'd in an -operative vibrating position lthere'on solely by the magnetic "forces which' areexer-tedon' -the central portion of' said diaphragrii; the periphery of" said aligning member havingxan outwardli projecting circular shoulder higher'than said seating ridge and holding said cover at a desired spacing from said diaphragm and 'determining the acoustic characteristics of saidtransmitting'space; said'raised circular surface region of saidseating ridge being adjoined by depressed" inner and outer circular regions thereof 'arranged'to givethe portion-of said ridge faeing said diaphragm: a curved convex crosssec'ti'on which-is' so shaped that a raised'circular region of saidseating ridge shall maintain'engage merit-with a continuous peripheral region of the diaphragm= throughout the normal l range of the vibratory-"amplitudesthereof;

In" a telephone receiver: amvibratory diaphragnihaving a generally circular periphery and a--gerrcra'll'v central magnetic armature portion;

acover 'wa'll including a soundoutlet duct and extending: over: the outer" side on the diaphragm: and forming with 'it an; acoustic transmitting"; space; a :relativelwmassivedriving'structure :com prising a substantially-rigid aligninggmembenhav l ing a continuous, generally-circular; outwardlyprojecting, rigid: seating ridge" of curved cross-- section against which aperipheralregion oi' ther inner side of said diaphragm restsand an electro'-' acoustic transducing structure includin'gmagnctic core portions secured to said aligning memberrand located opposite the inner side of saiddiaphmgm; said' core structure embodying-means' forexertingi unidirectional magnetic forces on the". central region of said diaphragm; saidtransducer struc-' ture including windings for inducing: withelec tric oscillations of the" principal "audioefrequency; range corresponding. vibratory magnetic forces exerted by said core: structure: on said: centrall region of saiddiaphragm; said'seatingridgehav ing a raised circular surface region engagedsby a peripheral regionof said diaphragm spaced'l radially' inwardly. away from the outer edge thereof; said. diaphragm beingheld pressed";

against said seating: ridge and being= maintained? in an operativevibratingposition thereon-solidibythe. magnetic iorcesuvhich are." exertedion the central portion of said diaphragm; the periphery: of said aligning-member-having arroutwardiy-prm .iecting circular shoulder higherthamsaid 'seating ridge and holding Said.COV8I"ELt*BJEGQSiIEGLSDECiHEjJf from said diaphragm and ldeterminingzthe ac'oustic'characteristics-of said transmitting spacersald: raised circular surface region 'of:s'aid=seating ridge being adioined'by depressed inner andiouterrcifi cular regions thereof arranged to give :the portion" of said'ridge facing-saiddiaphragm aicurvedfnona vex cross-section which is so shaped'thatraraised:v circular region of said seating ridge shallim'aintain engagement with a" continuous" peripheral region "of the diaphragm* throughout the normal-t rangeof the vibratory amplitudes thereof.

WILLIAM F. KNAUERT.

REFERENCES CIT-ED;

The following. references are' oizrecordf'in" the? file of this patent:

UNITED STATES PATENTS" 

